Hydraulic fuses



' Nov. 27, 1956 w. w. THOMAS HYDRAULIC FusEs Filed Jan. 7, 1953 ATTORNEY United States Patent O HYDRAULXC FUSES William W. Thomas, Chicago, lll., assignor to Wiiiiam Waterman, Evanston, Ill.

Application January 7, 1953, Serial No. 329,980

Claims. (Cl. 251-16) This invention relates to so-called fuses for altering or interrupting fluid iiow after a predetermined volume of uid has passed through the fuse.

The fuse of the present invention is sensitive only to iiow and will remain open until the flow aggregates a predetermined volume regardless of the number of interruptions which occur during the passing of such volume. The fuse will be opened and reset only by return or reverse flow, but will reset on a very small volume of return iiow compared to that necessary to close the fuse. The fuse valve, having low inertia, accelerates readily, and the fuse may therefore be made sensitive to a Wide range of flow rates; and its bulk density is the same as that of the Huid, thereby rendering it insensitive to external inertia and gravity forces. A simplified holding device prevents resetting of the fuse except on return ow.

The nature of the invention and further details thereof will be readily apparent from the following description of one illustrative fuse embodying the invention as shown in the accompanying drawing.

In said drawing:

Fig. 1 is a longitudinal section through the fuse;

Fig. 2 is a fragmentary longitudinal section on an enlarged scale of the improved holding device; and

Fig. 3 is a fragmentary section on an enlarged scale showing the mounting of the orifice to permit by-passing on return flow.

The illustrative fuse is an improvement over that shown in Stark Patent 2,592,487, reference to which is made for a detailed statement of the purpose and function of fuses of this character.

T he illustrative fuse is provided with inlet anclzoutletv fittings and 11 for connecting it (by conventional threaded couplings in this case) in a fluid line. The ma jor portion of the ow travels through the fuse unrestricted, entering at inlet 10 and directed by the conical head.

12 through the annular passage 13 leading to valve port 14, the latter surrounded by valve seat 15. A very small fraction of the iiuid (exactly proportional to that traveling unrestricted through passage 13) passes through metering orifice 16 (reaching it through one or more lateral or radial holes 17 in head 12) and displaces the valve piston 1S toward its seat at a rate proportional to the flow rate of uid through the fuse. The metering orilice is advantageously formed in a removable orice plate 19, loosely resting between bushing 21 and spacer 22 in head l2. Enough clearance is provided between the spacer; and bushing to allow the orifice plate to be lifted on re'- turn ot' piston 18 to permit the Huid freely to by-pass metering oriiice 16 (traveling around'the edge of plate 19), thereby to insure a rapid return or resetting of the piston with only a small fraction (e. g. 2%) of the total return ow. A spring retaining ring holds the bushing, spacer and orifice plate in assembled position.

The valve piston and connected parts are advantageously designed to have the same weight as the volume of uid they displace, thereby making the valve in etlect ice substantially weightless. This eliminates the tendency for the valve to be displaced by external forces such as gravity and inertia (depending upon the position of the fuse) and independently of flow. Heretofore, a light spring has been employed to exert a restraining force sufficient to prevent movement by such external forces, but such spring renders the fuse insensitive to low rates of flow having a pressure drop in the fuse insufficient to overcome the force of the spring. The spring being no longer necessary, the valve is responsive to very low flow forces and it is therefore possible to make it sensitive to any desired minimum ow rate.

In the present instance, the piston is given its low bulk density by making it hollow so that even though it be of metal (e. g. aluminum), its total weight (including attachments such asthe holding element in this case) is substantially equal to that of the volume of fluid displaced. Preferably, the cylindrical bearing face of the valve piston extends substantially throughout its length to eliminate binding against the cylinder wall.

The aforesaid holding device, which is in the form of a rod 26, is adapted to hold or lock the piston valve in any advanced position on interruption of llow, and to prevent its displacement by any force except the forces of either forward or return ow. The connection of rod 26 with the piston is preferably loose in a lateral direction, to make absolute concentricity of rod and piston unnecessary. A more detailed explanation of the purpose and function of a holding element of this character will be found in said Stark patent. A liow controlled gripper 27 holds the rod and piston 18 against movement. The gripper is of simplified form, comprising a pair of opposed spring fingers 28 mounted on the rod guide assembly 29. The pressure of each linger on the rod is balanced by that of the other, therefore eliminating any binding action on the valve piston which would increase the forces necessary to move the piston. Unbalanced lateral forces on the valve are very important where, as in the present instance, the valve is subject to high fluid pressures. Valves of this type are subject to working pressures of 3000 pounds per square inch and test pressures`% higher. Even slight unbalanced pressures are therefore magnified and may result in binding of the valve against the cylinder walls. The lingers normally grip rod 26 and are released by a cam 31 operated v by a ow sensitive member in the form of a piston 32.

Cam 31 is designed with opposed cam surfaces 33 to release the rod 26 upon longitudinal movement of cam 31 in either direction. Since the valve piston has substantially the same weight as the uid displaced, the gripper 27 need exert only a light gripping force on rod 26 to hold the piston against response to the aforesaid external forces. lease the rod by light forces, and it and its operating mechanism may be light and compact. This makes it possible to keep friction forces low and render the fuse sensitive (if that be desired) to the minute forces developed at low flow rates.

Piston 32 lies in the path of both forward and return ow, indeed it normally closes the passage between inlet and outlet and opens it only upon resumption of ilow in either direction. As here shown, flow from annular passage 13 passes through openings 34 in the sleeve 35 (which acts as the cylinder for piston 18) to reach valve port 14. Openings 34 are restricted only enough to produce a pressure drop suicient to actuate or displace valve 18 at minimum rates of ow. After passing the port 14, flow enters the annular space 37 around sleeve 35 through openings 36, and travels around the gripper assembly to ports 38 (controlled by piston 32) through which it reaches the outlet fitting 11. A seal in the form The gripper may therefore be actuated to re-` Yupon seating of valve i8 onV seat 15.

Piston 32 is normally Ycentered to 'close ports 3S by a relatively light spring 4l. Spring seats 42 and 43 com-V press the spring upon movement of piston 32 .in either direction. Both are s'lidabletowards each other on vthe cam rod '3i and are located inside spring'case 44 comprist ing a part of the valveV gripping assembly,

Fluid pressurevfrorn forward ow reaches the vcorn- Vpanion piston 45 (functionally integral with piston-3,2),

through openings 46, and displaces piston'32 (compressing spr-ing .41)Y toY uncover ports 3S to permit ow to reach outlet 11 through openings '47 inthe piston. Such movement kofthe piston Vsimultaneously Voperates cam-31 toirelease gripper Y27 to permit lforward, movement of the valve piston 18 ,in response to flow. 'Upon interruption of flow,

spring 4l returns piston S2 to close ports 33 and to ret apply gripper 27. Return how, reaching companion piston Y45 through openings '47, .also Vcompresses'spring Si by means of spring seat 42, moving piston 32 in the op-v posite direction to uncover ports 38 and to. release gripper 27. On interruption of return flowspring 41 returns piston32 to port closing position and re-applies gripper 27. rThus valve pistonjl is held against displacement in both directions by all forces except that of fluidriiow through the fuse. it will close on seat if and when the aggregate of successive 'forward flows (without intervening return ow) equals the predetermined volume for which the fuse is calibrated, The Aarea of piston 32 being large and spring 41 being light, only a very small ow'force is required to release the gripper. Pistons 32 and 45 are, however, light in weight, and spring 41'is su'icient to 'preventr movement of piston 32 in response, to Yinertia'and gravity forces. 'it should'be noted, nevertheless, that even thoughV gripper 27 be momentarily "released by excessive inertia forces, piston i8 (being in eifect Weightloss) would notV be substantially moved Vby suchexternal forces. t If it be desired to render the fuse insensitive to a cerf tain minimumrow, a small port 4% (here shown formed in piston 45) of a size sucient t0 ypass Such minimum flow, maybe employed to passvsuch minimum ow through the Vfuse without operating Ypiston 32.4 When Vtlow increases beyond such minimum Vitexertsenough force on piston 45 to operate piston-32m release valve piston 18. A by-p'ass port o'f jthis character may be employed, for example, to vrender the fusefinsensit'ive .to la small 'amount of harmlessleakage which sometimescannot be prevented. If the valvefis 4,to be sensitive-to all flow, 'the size of port t9 is of course zero. Y

The holding Vassembiy is rsecured in place by .an exterior rib 5l which Ylies between lthe end ofsleeve. 35 :and

sleeve 52, the latter serving. as a cylinder or guide for piston 32. l

The several sleeves 35 and '52 with their assemblies, are

secured in the surrounding fuse housing 455 by the shoulder 5d adjacent the outlet end of the fuse and by the inlet fitting l@ at the other end of the housing.

Obviously the invention is not limited to the details Vof the illustrative fuse, sincel these may be variously modied. `Moreover, it is not indispensable .that all the zfeatures of the invention be used conjointly, .sincevarious features maybe used to advantage in different combinasealed cylinder, substantially the weight of 'the vhydraulic iluidpassing through saidbore and displaced'by. said. valve piston whereby Vthe latter may beeasily :heldstationary against the forces of Vgravity and inertia, said valve piston `having 'a 'cylindrical bearing surface longer than its-diameter'and extending substantially the length of said valve piston to minimize the tendency Ito bind in said bore under inertia forces, a pair of opposed gripping lingers normally exerting opposed gripping forces on said valve piston to hold the same against movement, and an actuating mechanism responsive only to ow throughV said fuse for-releasing said fingers'. Y

2. Ahydraulic fuse sensitive Vto low rates of,t1uid flow comprisingin combination a'fuse housinghaving inlet and outlet-and a valve seat, a valve piston slidable in said housing toward vand away from said seat invresponse to I ow Vthrough said housing, said valve piston being sub- Ystantially the weight of the said fluid it displacesand thereby requiring only a slight force to hold it against movement by gravity'and inertia forces, a gripper comprising a4 pair of opposed gripper tingers normallyapplying .opposed Y andrbalanced .gripplngforces .to said valveppiston .tohold y the same against movement without-exerting unbalancedV lateral Vforces thereon, andV gripper actuating mechanism responsive only to flow for actuatingsaid gripper to re-A, j lease-said valve piston, saidimechanism having meansY operative-on,cessation 'ofA flow to restore saidv gripper to operative position. t

3. A hydraulic fuse sensitive to .low rates of uid flow comprising inV combination la Vfuse housing having inlet and outletiand la valve seat, avalve pistonslidable in said housing toward and awayfrom said seat in response toV ilow through .said housing, said Vvalve piston being substantiallythe weight` of the said fluid it displaces and thereby ,requiring Aonly lightl forces to hold theV same againstfmovementby gravity and inertia forces, .a'gripperi normally ,applyingopposed Vand balanced ,gripping forces t Vto. said v alve piston vto .hold lthe same 'againstV movement without Aexert-ing'any :unbalanced lateral force thereon, i and' gripper actuating Vrnechar'rismresponsive only to'ow for l actuating said gripper Vto release said valve piston.

4. In ..ahydraulic fuse for controlling lluidowthe Y combination comprising a fuse housing having aV uid passagethrough the same for said owand an inlet and outlet, Va ,valve seat and .a cylindrical bore adjacent said seatinsaid housing, aV piston .-valveslidable in Ysaid bore toward 'and away "from said seat in response toithe direc- Y tionA of tluidowV through saidpassage, and a ow re-- Sponsive'holdingdevice normally holding said piston valve againstrnovementgand actuated by ow in either direc'-Y tion to release said piston valve, said holdingdevicezhaving means normally applying opposed holding forces, to said piston valve, said pifston valve 'comprisingan elongated hollow sealed cylinder having substantially the same weight as the said Huid itdisplaces thereby requirirglittle -force :to .hold the same -against movement by inertia forces, said cylinder having a bearing faceV longer than ythedarneter of said cylinder .and extending substantially the length of saidk piston valve, and a Yconnecting .meansfor connecting said Ypiston to said holding device substantially within the'length of said bearing face to minimize thetendency of inertia'forces'to bind the pistoninfsaid-.bore

`5. In a hydraulic fuseforcontrolling iluid flow the f combination comprisinga fuse housing through which saidV -fluid ,flows and-"havinginletjand :outlet and a valve seat, vandia cylindrical -bore adjacent 'said seat, a piston valve slidablein said bore toward and away fromsaid seatin responseto the iow through said housing, said piston `valve comprisinga:hollowsealed cylinderlhaving substantiallyxthe weight-.of the said llluidit displaces whereby itrequiresonly alight force atofhold it against movement byisinertia ,and gravityforces, a'flow responsive holding 6 than the diameter of said cylinder and extending sub- References Cited in the file of this patent stantially the length of the piston valve to minimize the UNITED STATES DATENTS tendency to bind in said housing under inertia forces, 1 1 1 and a lost-motion connection for connecting said hold- 2 SSZ; A'Y l u lng devlce W1th sa1d cylinder and lying substantla y with 5 2,623,083 Schlumberger u Dec- 23 1952 in the length of said bearing surface. 

